Patent GB-1059687-A (GB)
Title: Optical brighteners
IPC: D06L3/12
Filed: 1965-04-29
Abstract: The invention comprises benzoxazoles of the formula <FORM:1059687/C2/1> in which R1 and R2, which may be identical or different, denote hydrogen or halogen atoms or alkyl or phenyl groups or together form an isocyclic ring of 2-5 carbon atoms. The benzoxazoles may be prepared by reacting 1 mol. of naphthalene - 1,4 - dicarboxylic acid dichloride with 2 mols. of o -aminophenol or an appropriately substituted o -aminophenol to yield a diamide of the formula <FORM:1059687/C2/2> which is then subjected to ring-closure by simple heating or by heating in a solvent in the presence of a catalyst, e.g. zinc chloride. Alternatively, a benzoxazole may be produced directly by heating 1 mol. of naphthalene-1,4-dicarboxylic acid with 2 mols. of an o -aminophenol either in an organic solvent in the presence of an acid catalyst, e.g. boric acid, or to 120-200 DEG  C. in polyphosphoric acid.  Specified o -aminophenols which may be used include o -aminophenol, 3 - amino - 4 - hydroxy - 1 - methylbenzene, 5 - amino - 4 - hydroxy - 1,2 - dimethyl - benzene, 3 - amino - 4 - hydroxy - 1 - tert. - butylbenzene, 5,6,7,8 - tetrahydro - 1 - amino - 2 - naphthol, 5 - amino - 6 - hydroxy - hydrindene, 3 - amino - 4 - hydroxydiphenyl 5 - chloro - 2 - aminophenol and 4,6 - dichloro-2-amino-phenol. Examples are given. The products are useful as optical brighteners (see Divisions C3 and D1).ALSO:As optical brighteners for shaped structures of synthetic materials, use is made of benzoxazoles of the formula <FORM:1059687/C3/1> in which R1 and R2, which may be identical or different, denote hydrogen or halogen atoms or alkyl or phenyl groups or together form an isocyclic ring of 2-5 carbon atoms (see Division C2).  Specified materials which may be treated are fibrous materials, films, foils and ribbons of polyamides of the polycaprolactam or nylon type, polyacrylonitrile, acetylcellulose, polyvinyl chloride, polyethylene, polypropylene, linear polyesters, e.g. polyethylene terephthalate, and polyacetals, which may be homo- or copolymers of formaldehyde or trioxane, some of which are specified.  The brighteners may be applied before or during the production of the synthetic materials or they may be applied to the finished product, suitably in an organic solvent or in aqueous suspension.  They may be used in association with oxidizing or reducing agents or detergents. Examples are given.ALSO:As optical brighteners for shaped structures of synthetic materials, use is made of benzoxazoles of the formula <FORM:1059687/D1-D2/1> in which R1 and R2, which may be identical or different, denote hydrogen or halogen atoms or alkyl or phenyl groups or together form an isocyclic ring of 2-5 carbon atoms (see Division C2).  Specified materials which may be treated are fibrous materials, films, foils and ribbons of polyamides of the polycaprolactam or nylon type, polyacrylonitrile, acetylcellulose, polyvinyl chloride, polyethylene, polypropylene, linear polyesters, e.g. polyethylene terephthalate, and polyacetals, which may be homo- or co-polymers of formaldehyde or trioxane, some of which are specified.  The brighteners may be applied in an organic solvent or in aqueous suspension.  They may be used in association with oxidizing or reducing agents or detergents. Examples are given.